That's right, 10°C only, because of holidays and not being home! On normal days, where I am at home, I am heating to a temperature between 22-23°C. I don't work all year, to stay at home with 3 Pullovers and five pairs of sockets and still be freezing, that is my opinion about it.
Well, my "house" is quite new, built in 2019, 15cm rock wool in walls, roof and floor, double glazing, it is a big "tiny house" with 50qm². Last winter was super smooth, had yearly costs of 600€ for heating and hot water (so, 50€ a month).
Energy costs at the moment 0.42€ / KwH for me. But the prices are really different since the war in Ukraine. Before it was quite stable around 0.30€ / KwH, now many people got letters from their electricity company, who are increasing the prices up to about 0.70€ / KwH. It is just crazy and for some people almost not payable anymore.
But as I can see, you are having the same problems in Finland, before Ukraine prices were around 0.10€ / KwH over there, right? Varying on the daily price of electricity? Here in germany, that model doesn't exist. The company, who is delievering the electricity to you, need to tell you a fixed price and guarantee that price for a specific period of a year, two years etc. (obviously with excusions, if for example the government is inventing a new tax).
But for that reason of high energy prices it is so great, that the Mitsurunner works so smooth.
5,82KwH for the last 24 hours, outside between -4 and -12°C, temperature in the house 9.5-10.5°C. That is just amazing!

Absoloutely worth the 50€ and a great idea, to try it with plug-adaptors, for not destroying the cables inside the Mitsu, for warranty reasons. Hope it works, if help is needed or a bigger order of flashed ESP32 is needed, you can send me a PN. I could offer, to buy the ESP32, flash it with Mitsurunner and send it to Finland, for final soldering / configuration, the only problem yet, that there is a shortage in WEMOS D1 ESP32 chips, also here in Germany.